PoolDoc's is the best answer. Teach them to swim. Not being able to touch the bottom is not a problem. My 3yr old grandson is learning how to swim in our pool this season. Right now he wears a swim vest that keeps him floating head/face up in case he looses balance in the pool. Of course we are always next to him. He dog paddles all around the pool with us close in tow. Your kids will learn to swim pretty quick as long as you take the time to teach them.

I suppose a submerged deck could also be built out of some of the new plastic decking material and don't forget a fence to separate the fall off area into the pool. It could even be of a temporary nature that could be removed easily when your kids learn to swim.

skeeter